Aspinall Unit operations update: Gunnison Tunnel diverting for the season

Gunnison Tunnel via the National Park Service

From email from Reclamation (Erik Knight):

Releases from the Aspinall Unit have been increasing over the last couple weeks as diversions to the Gunnison Tunnel have begun. So far these release changes have kept the flows in the Gunnison River through the Black Canyon around 630 cfs. Diversions into the Gunnison Tunnel are expected to increase again this week. This time releases from Crystal Dam will remain unchanged and Gunnison River flows will decrease accordingly. It is expected that river flows will decrease by 100-200 cfs this week. Currently snowpack in the Upper Gunnison Basin is at 72% of normal. The latest runoff volume forecast for Blue Mesa Reservoir projects 360,000 AF of inflow between April and July, which is 53% of average.

Flows in the lower Gunnison River are currently above the baseflow target of 890 cfs. River flows are expected to stay above the baseflow target for the foreseeable future.

Pursuant to the Aspinall Unit Operations Record of Decision (ROD), the baseflow target in the lower Gunnison River, as measured at the Whitewater gage, is 890 cfs for April and May.

Currently, diversions into the Gunnison Tunnel are 620 cfs and flows in the Gunnison River through the Black Canyon are around 630 cfs. By the end of the week Gunnison Tunnel diversions could be in the 700 to 800 cfs range and river flows could be in the 400 to 500 cfs range. Current flow information is obtained from provisional data that may undergo revision subsequent to review.

#Snowpack news: Aspinall Unit operations update — 650 CFS in the Black Canyon

Looking downstream from Chasm View, Painted Wall on right. Photo credit: NPS\Lisa Lynch

From email from Reclamation (Erik Knight):

Releases from the Aspinall Unit will be decreased by 100 cfs on Thursday, February 1st. Releases are being decreased in response to the very dry conditions and forecast for low spring runoff. Currently snowpack in the Upper Gunnison Basin is at 64% of normal. The latest runoff volume forecast for Blue Mesa Reservoir projects 420,000 AF of inflow between April and July, which is 62% of average.

Flows in the lower Gunnison River are currently above the baseflow target of 1050 cfs. River flows are expected to stay above the baseflow target for the foreseeable future.

Pursuant to the Aspinall Unit Operations Record of Decision (ROD), the baseflow target in the lower Gunnison River, as measured at the Whitewater gage, is 1050 cfs for January through March.

Currently, diversions into the Gunnison Tunnel are at 0 cfs and flows in the Gunnison River through the Black Canyon are around 750 cfs. After this release change Gunnison Tunnel diversions will still be at 0 cfs and flows in the Gunnison River through the Black Canyon will be around 650 cfs. Current flow information is obtained from provisional data that may undergo revision subsequent to review.

Aspinall Unit operations update: @USBR is drawing down Blue Mesa #ColoradoRiver #COriver

From email from Reclamation (Erik Knight):

Releases from the Aspinall Unit will be increased by 850 cfs between Friday, December 1st and Saturday, December 2nd. Releases are being increased as part of winter operations to lower the level of Blue Mesa Reservoir nearer to the winter elevation target as well as managing releases with consideration to wintertime hydropower demands.

Flows in the lower Gunnison River are currently above the baseflow target of 1050 cfs. River flows are expected to stay above the baseflow target for the foreseeable future.

Pursuant to the Aspinall Unit Operations Record of Decision (ROD), the baseflow target in the lower Gunnison River, as measured at the Whitewater gage, is 1050 cfs for December.

Currently, diversions into the Gunnison Tunnel are at 0 cfs and flows in the Gunnison River through the Black Canyon are around 750 cfs. After this release change Gunnison Tunnel diversions will still be at 0 cfs and flows in the Gunnison River through the Black Canyon will be around 1600 cfs. Current flow information is obtained from provisional data that may undergo revision subsequent to review.

Aspinall Unit operations update: Gunnison Tunnel diversions ending for season

From email from Reclamation (Erik Knight):

On Wednesday, November 1st, diversions to the Gunnison Tunnel will end for the season. Releases from the Aspinall Unit will be adjusted in coordination with the ramp down schedule for Gunnison Tunnel diversions in order to keep Gunnison River flows near the current level of 750 cfs. There could be fluctuations in the river throughout the day until the Gunnison Tunnel is completely shut down.

On Thursday and Friday, November 2nd and 3rd, releases from the Aspinall Unit will be reduced to 300 cfs during the day time hours in order to allow for completion of the sonar survey of the Crystal Dam stilling basin. Gunnison River flows will drop down towards 300 cfs during the day while returning to 750 cfs during the non-working hours. After the sonar survey is completed at the end of the day on November 3rd, river flows will return to the current level of 750 cfs.

Flows in the lower Gunnison River are currently above the baseflow target of 1050 cfs. River flows are expected to stay above the baseflow target for the foreseeable future.

Pursuant to the Aspinall Unit Operations Record of Decision (ROD), the baseflow target in the lower Gunnison River, as measured at the Whitewater gage, is 1050 cfs for October through December.

Currently, diversions into the Gunnison Tunnel are near 850 cfs and flows in the Gunnison River through the Black Canyon are around 750 cfs. After the shutdown of the Gunnison Tunnel and completion of the Crystal stilling basin sonar survey, flows in the Gunnison River through the Black Canyon will return to 750 cfs. Current flow information is obtained from provisional data that may undergo revision subsequent to review.

Aspinall Unit operations update: Lower Gunnison streamflow above baseflow target

Fog-filled Black Canyon via the National Park Service

From email from Reclamation (Erik Knight):

Releases from the Aspinall Unit will be decreased by 100 cfs on Thursday, October 12th. Diversions to the Gunnison Tunnel will be reduced by 100 cfs on Wednesday, October 11th so there will be a short period of flows over 1000 cfs in the Gunnison River through the Black Canyon before the river returns to a flow of 950 cfs by late Thursday morning.

Flows in the lower Gunnison River are currently above the baseflow target of 1050 cfs. River flows are expected to stay above the baseflow target for the foreseeable future.

Pursuant to the Aspinall Unit Operations Record of Decision (ROD), the baseflow target in the lower Gunnison River, as measured at the Whitewater gage, is 1050 cfs for October through December.

Currently, diversions into the Gunnison Tunnel are near 975 cfs and flows in the Gunnison River through the Black Canyon are around 950 cfs. After this release change Gunnison Tunnel diversions will be about 900 cfs and flows in the Gunnison River through the Black Canyon will still be around 950 cfs. Current flow information is obtained from provisional data that may undergo revision subsequent to review.

@USBR needs to draw down Blue Mesa to meet winter target, water for Lake Powell

From The Grand Junction Daily Sentinel (Gary Harmon):

Blue Mesa this week was brimming at 99 percent full and it was far from alone among Colorado River Basin reservoirs.

Morrow Point and Crystal reservoirs below Blue Mesa on the Gunnison River were 96 percent and 90 percent full, respectively.

“It’s going to take a lot of work” to reduce Blue Mesa’s level to 70 percent of full, or 580,000 acre-feet of water, U.S. Bureau of Reclamation hydrologist Eric Knight said Thursday.

Typically, all three reservoirs are well depleted by this time of year to meet irrigation demand, as well as feeding more water into Lake Powell, the largest storage unit in the Upper Colorado River Basin.

This year, however, river managers learned late that there was more snow in the high Colorado mountains than they had believed when deciding how much water to release early on this spring, officials said during a regular update on management of the Aspinall unit.

Several factors contributed to the underestimation of snowpack, not least of them the warm March in the Colorado Rockies and the fact that some snow-monitoring gauges were covered with snow, incapable of providing accurate information, officials said.

Recent storms in the high country also have pumped more water into the reservoirs.

River managers have to balance the need to release more water out of the Aspinall unit with making sure that the Gunnison doesn’t overflow its banks in Delta.

At the same time, managers also have to get as much water as possible into Lake Powell, which can hold some 24 million acre-feet of water but which now holds about 15.2 million acre-feet.

The Bureau of Reclamation this year is to release 9 million acre-feet of water into Lake Mead.

Aspinall Unit operations update: 1150 CFS in Black Canyon

Fog-filled Black Canyon via the National Park Service

From email from Reclamation (Erik Knight):

The spring peak operation has officially concluded. Due to an issue with the power plant at Crystal Dam, the ramp down was forced to end prematurely. As of today releases are being made through the bypass gates at a rate of 2150 cfs. This has put flows in the Gunnison River through the Black Canyon around 1150 cfs. This release rate is expected to continue for the foreseeable future. Further adjustments to this release rate may be necessary to manage the remaining runoff coming into Blue Mesa Reservoir.